ABSTRACT
Disrupted-in-schizophrenia 1 (Disc1) is a key molecular driver for the biology of mental diseases. In order to investigate its role in brain function, we previously generated mice lacking exons 2 and 3 of Disc1 on a C57BL/6J genetic background (Disc1Δ2-3/Δ2-3 mice), which have a deficiency of the full-length Disc1 protein. In the present study, we examined the role of Disc1 in cognitive function using a touchscreen-based visual discrimination (VD) task in which mice had to discriminate 1 of 2 stimuli simultaneously displayed on the screen and received a liquid reward. Disc1Δ2-3/Δ2-3 mice showed impaired performance in the VD task, and this was mainly attributed to the perseverative response being significantly stronger than that in wild-type (WT) mice. Furthermore, the numbers of marbles buried in the marble burying test and nestlets shredded in the nestlet shredding test by Disc1Δ2-3/Δ2-3 mice were significantly higher than those by WT mice, suggesting perseverative/compulsive behaviors by Disc1Δ2-3/Δ2-3 mice. A treatment with clozapine ameliorated behavioral deficits in the VD and marble burying tasks. c-Fos expression was significantly stronger in the dorsomedial striatum (DMS), but not the dorsolateral striatum (DLS) after the first VD session in Disc1Δ2-3/Δ2-3 mice than in WT mice. The treatment of mice that had previously expressed hM3Dq in the DMS with clozapine-N-oxide (CNO) impaired performance in the VD task. These results suggest that cognitive impairments accompanied by perseverative/compulsive behaviors in Disc1Δ2-3/Δ2-3 mice are associated with hyperactivity of the DMS.
